1. Field of the Invention
The present invention relates to a medical appliance driving apparatus designed to expand and contract a medical appliance such as an artifial heart pump or an intraaorta balloon pump by alternately supplying positive and negative pressures thereto. More particularly, the present invention pertains to an apparatus for driving an intraaorta balloon pump.
2. Description of the Related Art
Medical appliance driving apparatus are demanded to increase the speed of expansion and contraction of the associated medical appliances. It is preferable, in order to meet such requirements, to make steep the rise (or fall) of the pressure supplied to the medical appliances. For this reason, one type of driving apparatus employs an accumulator to prevent variations in pressure. However, it is necessary to considerably increase the capacity of the accumulator in order to absorb a rise or lowering in pressure produced in the accumulator when the state of the medical appliance is changed from expansion to contraction or vice versa. Accordingly, it is difficult to reduce the overall size of the driving apparatus.
There is another type of medical appliance driving apparatus wherein a solenoid valve is disposed in parallel to a pressure regulating valve and a pressure from a pressure source such as a compressor or a vacuum pump is directly supplied to the medical appliance by controlling the solenoid valve so as to be opened and closed at a predetermined timing, thereby making compensation for the rise of pressure supplied to the medical appliance.
For example, a driving apparatus disclosed in Japanese Patent Laid-Open No. 177062/1984 is arranged such that, while a negative pressure is being supplied to a medical appliance, a positive pressure is directly led from a compressor through a solenoid valve and kept higher than a set pressure regulated by a pressure regulating valve to thereby compensate for the rise of pressure when a positive pressure is supplied to the medical appliance.
Driving apparatus disclosed in Japanese Patent Laid-Open Nos. 206698/1984 and 207158/1984, respectively, are arranged such that, when a positive pressure is supplied to a medical appliance, a positive pressure from a compressor is directly supplied through a solenoid valve for a predetermined period of time to thereby compensate for the rise of pressure supplied to the medical appliance.
Driving apparatus disclosed in Japanese Patent Laid-Open Nos. 206699/1984 and 207158/1984 are provided with an auxiliary accumulator for accumulating a positive pressure from a compressor in addition to an accumulator for accumulating a regulated pressure, and when the regulated pressure is supplied to the medical appliance, the pressure accumulated in the auxiliary accumulator is supplied together with said regulated pressure to thereby make compensation for the rise of pressure supplied to the medical appliance.
A driving apparatus disclosed in Japanese Patent Laid-Open No. 106462/1985 is arranged such that, when a positive pressure is supplied to a medical appliance, a positive pressure from a compressor is directly supplied through a solenoid valve to thereby compensate for the rise of pressure supplied to the medical appliance, and when the pressure in the medical appliance reaches a predetermined value, the solenoid valve is closed.
In all of these driving apparatus, a pressure from a pressure source is directly led to a medical appliance in order to compensate for the rise of pressure supplied to the medical appliance. Accordingly, when the medical appliance is to be expanded, a positive pressure fluid is needed to compensate for a negative pressure in the pipe line or the like, whereas, when the medical appliance is to be contracted, a negative pressure fluid is needed to compensate for a positive pressure in the pipe line. For this reason, it has heretofore been unavoidable that the rise of pressure at the time of switching the state of the medical appliance from expansion to contraction and vice versa is somewhat slow.